Sunday, July 28, 2013

Two people came in at different times this week worried about a white pigeon hanging around a bird feeder. These all white pigeons were banded and friendly but not friendly enough to catch. Pigeons that are all white are used commonly for “Dove” releases. If you can approach them and gently pick them up to read there leg tag it might have a phone number to call and return the bird.

Or sometimes the pigeon’s owner can be traced through the National Pigeon Association’s (NPA) website at www.npausa.com; it has details on identifying
owners. If the bird hangs around for more than 48 hours and refuses to leave,
and the owner cannot be located, call local dove release businesses for
information or visit the American Racing Pigeon Union’s website.

Once released these pigeons usually have the ability to fly straight home. For one reason or another some birds take a little detour from their path. Experiments with homing pigeons are still going on today to discover how their homing ability works.

Scientists have focused their attention in three areas: the beak, the inner ear and the eyes. Birds’ beaks contain tiny grains of magnetite, a form of iron oxide which is magnetized easily to help birds point north. But when David Keays of the Institute of Molecular Pathology in Vienna examined the beaks, he found that the magnetite grains were mostly located in macrophages, which wander around the body, rather than in specialized sense cells. This strengthened the case that birds’ magnetic sense resides not in their beaks, but in tiny concentrations of iron in the neurons of a pigeon’s inner
ear.

Case closed? Not quite. The latest research, published in June, suggests the beak
does have a role to play after all. Researchers led by Henrik Mouritsen of the University of Oldenburg
in Germany
found that the beak detects the angle of the Earth’s magnetic field with the
ground, which varies with latitude and may be used by birds as part of their
mapping sense.

However, there is also evidence that magnetic sensing relies on
chemical reactions in birds’ eyes. It seems to involve a region the brain
called cluster N, which is connected to the eyes. Cluster N is also more active
when birds are using their magnetic sense. One theory, advanced
by Klaus Schulten of the University of Illinois and Urbana-Champaign, is
that a retinal protein that is split into two magnetically sensitive molecules co-operate, even when separated,
to detect variations in the magnetic field. This might allow birds to see
patterns of spots that remain stationary as they turn their heads, to indicate
magnetic direction.

In the end, how birds sense magnetic fields to create a natural
version of the global-positioning system is still not understood fully. It is
possible that all three of these mechanisms work together. But having made
rapid progress in the field in recent years, scientists do finally seem to be
homing in on the answer.